Control for glass marble, feeding, melting, and fiber forming unit

ABSTRACT

An automatic output control whereby the output of an inorganic thermoplastic material melting and fiber forming unit is controlled by adjusting the amount of heat applied to the melting unit in accordance with a control signal. The control signal is derived by comparing the actual rate of thermoplastic material entering the melting and fiber forming unit with a desired standard.

United States Patent 1191 Ramge Dec. 118, 1973 CONTROL FOR GLASS MARBLE,FEEDING, MELTING, AND FIBER FORMING UNIT [75] Inventor:

[73] Assignee: Johns-Manville Corporation, New

York, N .Y.

22 Filed: Jan.27, 1972 21 Appl. No.: 221,314

Dennis Lee Ramge, Waterville, Ohio [52] U.S. C1 65/9, 65/158, 65/162,

[51] Int. Cl. C03c 3/00, C03c 37/00 [58] Field of Search 65/162, 163,164, 65/158, 335, 9

[56] References Cited UNITED STATES PATENTS 3,573,017 3/1971 Griem, Jr65/162 X 3,134,145 5/1964 Miller 19/155 Primary ExaminerArthur D.Kellogg Attorney-John A. McKinney et al.

[ 5 7] ABSTRACT An automatic output control whereby the output of aninorganic thermoplastic material melting and fiber forming unit iscontrolled by adjusting the amount of heat applied to the melting unitin accordance with a control signal. The control signal is derived bycomparing the actual rate of thermoplastic material entering the meltingand fiber forming unit with a desired standard.

8 Claims, 2 Drawing Figures PATENTEUDEEI 8 I975 FIG. 1

FIG. 2

CONTROL FOR GLASS MARBLE, FEEDING, MELTING, AND FIBER FORMING UNITSUMMARY OF THE INVENTION This invention relates to the control of theoutput quantity of secondary material by determining the rate of inputof primary material to the process. More particularly, the inventionconcerns the production of filaments of inorganic thermoplastic materialby automatically controlling the output from melting and fiber formingunits to predetermined levels using the rate of input of uniformdiscrete increments of material.

The state of the art in making a thermoplastic filament product hasalways recognized the desirability and need for having a constantquantity of heatsoftenable material for the rest of the process to workupon. A more consistent and constant quanity is possible when the outputis maintained at a predetermined level, not only on a total machinebasis, but also on a sequented individual equipment basis. Many of theprocess problems can be directly related to the individual melting andfiber forming units whose outputs can differ greatly even though thetotal of their outputs is correct. This difference in individual melteroutputs also causes final products with undesirably large toleranceranges. In order to change the output from a demand feed melter theamount of thermal energy available must be increased or decreased. Thiswill alter the viscosity of the material and thus the output for a givenhead. In a manual adjustment system a period of cycling will occur inwhich the product is nonuniform and therefore of poor quality. Suchnonuniformity is evidenced in felted wool produced by flame attenuationof primary fibers of glass drawn from a plurality of glass melting andfiber forming pots as a blanket of varying density and/or final fiberdiameter across its width wherein low density material and/or fiberdiameters finer than desired are formed in the region supplied fibers bya pot having a reduced output while excessive densities and/or fiberdiameters greater than desired are formed in the region supplied by apot having an excessive output.

In the present invention the change in the quantity of heat energy inputis-automatically controlled to provide the desired output from the glassmelting units. This is accomplished by monitoring the rate of input ofglass to the melter and generating a correction signal by comparing theinput with a predetermined standard.

It is an object of this invention to provide an improved method andapparatus for automatically controlling a fiber forming system tomaintain maximum product quality and maximum operating efficiency.

It is another object to provide an improved method and apparatus forcontinuously melting heat-softenable materials for use in a fiberforming process in which the rate of inorganic thermoplastic materialinput is used as the measure of the total material flow through amelting unit and the process is controlled accordingly.

It is a further object of this invention to provide an improved methodand apparatus for insuring the consistency of a single product made fromseveral material melting and fiber forming units by controlling theirindividual outputs.

DESCRIPTION OF THE DRAWINGS FIG. l is a combination block diagram andschematic elevation view of a glass melting and fiber forming unitillustrating the proposed method of control; and

FIG. 2 is a schematic plan view of a machine for forming felted glassblanket by flame attenuation of primary filaments from a plurality ofglass melting and fiber forming units each controlled according to FIG.1, and illustrating in an exaggerated manner the effect of operating oneunit of a group at an output different from the uniform output of theremaining units as it refleets upon the blanket density and/or fiberdiameter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates atypical embodiment in a glass process. A glass melting unit 11 receivesglass marbles 12 from a hopper 13 where they are stored. The glassmarbles 12 either drop or roll past a sensor, in the example an energysource 14 and detector 15 such as a light beam and photoelectric cell.The passing marbles modulate the output of the detector and continueinto an inclined chute 16 which directs them into the upper end of themelting unit. The melting unit accepts the marbles on a supply demandbasis. As the marbles melt, a demand is put on the chute for moremarbles and the supply hopper then must release the quantity required tokeep the chute full. A source of high-temperature thermal energy such asburners 17 heats and softens marbles within the melting unit 11 untilthe viscosity of the softened glass is such that the glass can beextruded from the melting unit in the form of primary fibers 18 whichare conditioned by pulling rolls 19. The primary fibers 18 can be formedinto secondary fibers as by softening and attenuating them with anattenuation burner, and collecting the fibers on a collecting apparatussuch as a moving conveyor as will be discussed generally with respect toFIG. 2.

The modulated output from the detector is a succession of pulses whichmay be random, one pulse for each increment of glass which is passed tothe melting unit ll]. This output is supplied to a control unit 21. Thepulses are summed by a count accumulator 22 over a fixed period of timewith an output proportional to the number of counts received. Alsowithin the control unit is an input count set point 23 which permits thesetting of the number of marbles desired in the fixed period of time.The output from the count accumulator and the input count set point aresent to a comparator 24 where a plus or minus error signal is generated.This error signal then passes through a normally closed relay 25 as anoutput signal.

A condition may occur where the detector does not issue a count for aspecified period of time resulting from either the continued presence orabsence of a marble between source 14 and detector 15 as where a jam ofmarbles occurs in chute 16 or hopper 13. The marble jam alarm 26 sensesthis condition and opens normally closed relay 25 so that the errorsignal cannot pass. At the same time the marble jam alarm actuates analarm indicator 27 to alert the operating personnel. After the troubleis corrected the marble jam alarm is reset and the normally closed relayallows the error signal to pass. Since ajam may clear after an alarmcondition is established, the count accumulator is arranged to continuemonitoring the input to the melter unit so that, upon reset, theaccumulated data is available for control.

The error signal is received by attenuator 28 which passes only afraction of the total signal. Attenuator 28 may take the form of anormally open interrupt timer which cycles with a pattern that allowsthe error signal to pass for a set period of time during each cycle. Asan example, the interrupt timer might pass the signal for one secondevery minute. The attenuated error signal is then used to control anadjustable source of thermal energy such as adjustable gas valve 29which regulates the quantity of air-gas mixture flowing to burners 17thereby controlling the melting rate. The attenuator is used to preventovershoot which would cause undersirable oscillations each time the rateof input of marbles changed.

Since the set point represents the desired feed, a plus error representsa feed rate greater than the set point and dictates a reduced meltingrate and thus a reduced input of thermal energy to the melting unit.Accordingly, a plus error reduces the rate of input of the combustiblemixture to burners 17 and a minus error increases that rate in theexample.

Overshoot of the thermal energy input and hunting of the control as aresult of such overshoot is reduced beyond that achieved by the effectof the attenuator 28 by providing the control with a dead band. Such adead band can be introduced in the comparator 24 by preventing it fromissuing an error signal when the count accumulator signal is within agiven range of the set point. Alternatively, the dead band can beintroduced by rendering the control of the thermal energy supply nonresponsive to error signals below a given level. In either instance, thedead band should be of adjustable width and should be adjustable aroundthe set point.

By determining the average weight of the marbles entering the system theinput count set point 23 can be adjusted to provide a desired weight ofglass per hour. The control unit then will provide information to thesystem to enable it to adjust the thermal energy input and thus themelting rate so that the melting unit 11 will accept, melt and issue thedesired weight of glass per hour.

This system may be used advantageously where a number of materialmelting and fiber forming units are combined to produce a singleproduct. For example, by controlling the output of each unit in aninsulation blanket forming process a mat of uniform density and- /orfiber diameter can be produced. Further, changes of product from a givenmachine can be accomplished more effectively than in the past sincepredetermined set points can be established for each melter-fiber formerpot and the controls will expeditiously establish uniform output acrossthe width of the machine by individually adjusting each pot inaccordance with the rate at which the essentially equal sized glassincrements (marbles) are fed to the pot to control the amount of heatapplied to said unit by its respective heating means whereby the rate atwhich fiber is deposited in said receiving apparatus at locations acrosssaid apparatus is adjustable.

FIG. 2 illustrates a particularly advantageous use of a plurality of themelter-fiber forming units disclosed in FIG. 1 to improve the control ofmaterial distribution across the width of a felted blanket of glassfiber. Convcntionally, a plurality of pots 11 in which glass marbles aremelted and from which primary fibers are drawn are arrayed transverse ofa line along which attenuated fibers are formed into a blanket.Attenuation burners 31 are associated with each pot to soften, attenuateand entrain the attenuated fibers in a blast of gas and fiber confinedand directed into a collection hood 32 which collects the fibers over acollecting chain 33 having behind its collecting face a suction box 34from which gas is withdrawn by blower 35. The screen is trained over endrolls 37 and is endless. lts delivery end from which the collectedblanket of glass is removed is not shown.

In operation the burner blasts pass beneath the pull rolls 19 below eachpot and in general tend to carry the attenuated secondary fibers fromtheir respective pots along a path aligned with the respective pot andprimary filaments depending therefrom. Accordingly, while somedisplacement of fibers transverse of the line of travel from the fiberformers will occur there is a Stratification of the preponderance offibers from individual fiber formers as laid down in a blanket on thecollecting chain 33 downstream of the fiber formers. This Stratificationof fibers is illustrated in FIG. 2 as a low density band issuing fromthe second unit 11 and can result in an unsatisfactory product whereuniformity is desired and where the fiber formers of the array are notissuing uniform amounts of glass as primary fibers to the burners. Thus,where a uniform density and diameter of fiber across the width of thefiber receiving apparatus, the collecting chain 33, is desired, each ofthe fiber formers should issue fiber at a uniform rate. Usually it isdesired that they all issue fibers at a uniform rate. However, there canbe instances where controlled density and/or diameter of the fibersfelted into the blanket in strips of different fiber density and/ordiameter across the width of the collecting chain is desirable and thefiber formers disposed across the array can be adjusted to issue fibersat different rates to provide these controlled variations.

The individual control of the heat input as established by an adjustableset point or reference signal is therefore used to advantage for each ofa plurality of melter-fiber former units in producing an end product ofcontrolled characteristics composed of a combination of the fibersproduced by the individual units at a point in the production at whichcontrol was not available heretofore. I

The adjustment of the input of thermal energy in response to the rate ofinput of the material to be melted can be contolled over a range for agiven melting unit to adjust the diameter of the primary filamentsissuing from the unit. The diameter of the primary filaments is afunction of the throughput in the case of glass since those filamentsare issued at essentially the same velocity for all throughputs in theusual operating range of a unit. However, secondary fiber diameter canbe controlled by control of the operating parameters of the attenuatingmeans. ln the case of attenuating burners a higher velocity outputreduces secondary fiber diameter. Thus, when attenuating control iscombined with the throughput control discussed above, secondary fiberdensity can be controlled while secondary fiber diameter is controlledto increase or decrease density with a constant fiber diameter, to alterdensity while altering fiber diameter, or to maintain density whilealtering fiber diameter.

lt is to be understood that the present control system for melter-fiberformer units is adaptable to materials other than glass and to feedincrements other than uniformly sized marbles of glass. Further thevarious elements including heat sources for the melting units,detectors, set point controls, signal comparing means and attenuatorsare available in many forms. Accordingly, the above disclosure is to beread as illustrative of the invention and not in a limiting sense.

I claim:

1. A fiber forming apparatus wherein glass marbles are fed into a fiberforming unit comprising:

a. heating means for heating the unit to melt the marbles,

b. conveying means for conveying the marbles from a source to said fiberforming unit with the rate of feed of the marbles into said unit beingregulated by the rate at which the marbles are melted in said unit, and

c. control means comprising means for counting the marbles duringpassage of said marbles from said source to said unit on said conveyingmeans and for generating a control signal which is a function of thenumber of the marbles counted, reference signal means for producing areference signal characteristic of a given rate of passage, said meansfor producing a reference signal being adjustable to enable selection ofa desired rate for comparison with said control signal, comparator meansfor comparing said reference signal with said control signal and forissuing an error signal which is proportional to the difference betweensaid control signal and said reference signal, and means responsive tosaid error signal for controlling said heating means to regulate theheat input to said fiber forming unit.

2. An apparatus as defined in claim 1 in which said means for countingthe marbles comprises a radiant energy source and detector positioned onopposite sides of said conveying means and arranged to generate a pulsefor each marble which passes along said conveying means.

3. An apparatus as defined in claim 1 including indicator meansresponsive to a signal characteristic of the absence of the passage ofmarbles through said conveying means at at least a certain rate.

4. An apparatus as defined in claim 3 wherein said indicator meansresponsive to the absence of the passage of marbles at at least acertain rate is responsive to a stoppage of the passage of the marbles.

5. An apparatus as defined in claim 1 in which said means to generate anerror signal includes means to attenuate said error signal.

6. An apparatus as defined in claim 1 including means responsive to asignal characteristic of the absence of the passage of marbles throughsaid conveyance means at at least a certain rate to prevent the responseto said error signal of said means for controlling said heating means.

7. An apparatus as defined in claim 1 comprising a plurality of saidfiber forming units each unit having one of said heating means, one ofsaid conveying means and one of said control means.

8. An apparatus as defined in claim 7 wherein:

a. fiber collecting means is provided to receive fiber from said fiberforming units, and

b. said fiber forming units are disposed across a width of said fibercollecting means whereby the output of said fiber forming units can beregulated by said control means to regulate the amount of fibersdeposited on said collecting means in regions located across the widthof the fiber collecting means.

1. A fiber forming apparatus wherein glass marbles are fed into a fiberforming unit comprising: a. heating means for heating the unit to meltthe marbles, b. conveying means for conveying the marbles from a sourceto said fiber forming unit with the rate of feed of the marbles intosaid unit being regulated by the rate at which the marbles are melted insaid unit, and c. control means comprising means for counting themarbles during passage of said marbles from said source to said unit onsaid conveying means and for generating a control signal which is afunction of the number of the marbles counted, reference signal meansfor producing a reference signal characteristic of a given rate ofpassage, said means for producing a reference signal being adjustable toenable selection of a desired rate for comparison with said controlsignal, comparator means for comparing said reference signal with saidcontrol signal and for issuing an error signal which is proportional tothe difference between said control signal and said reference signal,and means responsive to said error signal for controlling said heatingmeans to regulate the heat iNput to said fiber forming unit.
 2. Anapparatus as defined in claim 1 in which said means for counting themarbles comprises a radiant energy source and detector positioned onopposite sides of said conveying means and arranged to generate a pulsefor each marble which passes along said conveying means.
 3. An apparatusas defined in claim 1 including indicator means responsive to a signalcharacteristic of the absence of the passage of marbles through saidconveying means at at least a certain rate.
 4. An apparatus as definedin claim 3 wherein said indicator means responsive to the absence of thepassage of marbles at at least a certain rate is responsive to astoppage of the passage of the marbles.
 5. An apparatus as defined inclaim 1 in which said means to generate an error signal includes meansto attenuate said error signal.
 6. An apparatus as defined in claim 1including means responsive to a signal characteristic of the absence ofthe passage of marbles through said conveyance means at at least acertain rate to prevent the response to said error signal of said meansfor controlling said heating means.
 7. An apparatus as defined in claim1 comprising a plurality of said fiber forming units each unit havingone of said heating means, one of said conveying means and one of saidcontrol means.
 8. An apparatus as defined in claim 7 wherein: a. fibercollecting means is provided to receive fiber from said fiber formingunits, and b. said fiber forming units are disposed across a width ofsaid fiber collecting means whereby the output of said fiber formingunits can be regulated by said control means to regulate the amount offibers deposited on said collecting means in regions located across thewidth of the fiber collecting means.